Thermally resistant resin composition and method for miscible preparation

ABSTRACT

The present invention provides a thermally resistant resin composition containing PS and PPO, wherein at least one of PS and PPO has an acid group and the acid group is neutralized with a basic metal compound containing a metal element of the group 2B, 3B, 4B or 5B of the periodic table; thermally resistant PS and PPO each with an acid group which is also neutralized in the same manner as described above; and a method for miscible preparation of PS and PPO, wherein at least one of PS and PPO has an acid group and the acid group is neutralized similarly.

This application is a divisional application of Ser. No. 08,699,936filed on Aug. 20, 1996 and now U.S. Pat. No. 5,981,657.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermally resistant resin compositioncontaining polystyrenes (PS) and polyphenylene oxides (PPO).

2. Prior Art

Resin compositions produced by blending PS with a glass transition point(Tg) of about 100° C. and PPO with Tg of about 210° C. together, havebeen known widely as one class of thermally resistant polymer alloys ina uniformly miscible system. The PS/PPO resin compositions have singleTg approximately corresponding to the arithmetic mean of the Tgs of thetwo polymers.

Because PS/PPO resin compositions show excellent electric performancesuch as dimensional stability, mechanical properties, insulatingproperties and high-frequency performance, furthermore, the compositionsare utilized in resin molded articles such as housings of electricappliances and electronic devices including television sets, airconditioning systems, computer systems; chassis for office appliancesfor example copying machine and facsimile; various containers (trays andthe like); and automobile parts such as instrument panel.

Such PS/PPO resin compositions do not generate hazardous substances suchas corrosive gases and dioxin during combustion because the compositionsdo not contain halogen atoms. In that sense, the compositions are fairlysafe. Additionally because PS/PPO resin compositions have excellentthermoplasticity, the compositions can be melt again after the moldingprocess to be put to re-molding process. Thus, PS/PPO resin compositionsare considered as recyclable resources. Hence, the utility (applicablerange) of PS/PPO resin compositions has been expected to be enlargedfrom the enhanced need in recent years to preserve the globalenvironment.

The field of the materials for printed board requiring soldering heatresistance (180° C.) is included in one of their applicable range to beenlarged.

Conventional materials for printed board include for example a compositematerial such as glass epoxy resin-immersed paper and phenolresin-immersed paper, but it is difficult to separate the individualmaterials constituting these composite materials. Furthermore, theresins used therein are thermosetting. Therefore, these materials aredisadvantageous in that reprocessing (recycling) of these materials viamelting is substantially impossible while PS/PPO resin compositions canbe recycled. Accordingly, it has been desired to use recyclable PS/PPOresin compositions as printed board materials instead of conventionalmaterials for printed board.

However, the glass transition point of conventional PS/PPO resincompositions corresponds to the arithmetic mean of the Tgs of the twopolymers, so that a higher content of PS causes lower Tg compared withthe Tg of a resin of 100% PPO. Thus, the heat resistance of PS/PPO resincompositions is poorer than that of the resin of PPO alone.

So as to improve the heat resistance of PS/PPO resin compositions,alternatively, it is proposed to improve the glass transition point ofthe compositions by introducing a sulfonic acid group into either one orboth of PS and PPO and reacting sodium methoxide with the sulfone groupto form an ionic bond between the polymer chains (Don-Tsai Hseih et al.,Polymer, Vol.33, No. 6, 1210 (1992)).

OBJECTS AND SUMMARY OF THE INVENTION

The heat resistance of PS/PPO resin compositions with an ionic bondintroduced by reacting a sulfonic acid group with sodium methoxide isstill not sufficient. Therefore, further improvement of the heatresistance is desired.

When an acid group such as sulfonic acid group is introduced into eitherone of PS and PPO, the miscibility of the two may decrease depending onthe type and concentration of the acid group. Hence, it is needed tomake the two readily miscible irrespective of the type of the acid groupand the like.

In addition to these needs, it is also desired to improve the heatresistance of each of PS and PPO.

The present invention is to overcome the problems of prior art. It is anobject of the present invention to further improve the heat resistanceof PS/PPO resin compositions. Also, it is an object of the presentinvention to improve the heat resistance of each of PS and PPO. Stillfurthermore, it is an object of the present invention to make PS readilymiscible with PPO.

So as to improve the heat resistance of a thermally resistant resincomposition containing PS and PPO, the present inventors have found thatthe heat resistance of the thermally resistant resin composition canfurther be improved by introducing an acid group into PS or PPO or both,and neutralizing the acid group with a basic metal compound containing ametal belonging to the group 2B, 3B, 4B or 5B of the periodic table toform an ionic bond. Thus, the invention has been achieved.

More specifically, the present invention is to provide a thermallyresistant resin composition containing PS and PPO, wherein at least oneof PS and PPO has an acid group and the acid group is neutralized with abasic metal compound containing a metal element of the group 2B, 3B, 4Bor 5B of the periodic table.

Furthermore, the present invention is to provide PS with an acid group,wherein the acid group is neutralized with a basic metal compoundcontaining a metal element of the group 2B, 3B, 4B or 5B of the periodictable. Additionally, the present invention is to provide PPO with anacid group, wherein the acid group is neutralized with a basic metalcompound containing a metal element of the group 2B, 3B, 4B or 5B of theperiodic table.

Still furthermore, the present invention is to provide a method formiscible preparation of PS and PPO, wherein at least one of PS and PPOhas an acid group and the acid group is neutralized with a basic metalcompound containing a metal element of the group 2B, 3B, 4B or 5B of theperiodic table.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows graphs depicting the dynamic elastic moduli (tan δ) of theresin compositions of Example B3, Comparative Examples B5 and B6 vstemperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail.

The thermally resistant resin composition containing PS and PPO inaccordance with the present invention is produced by reacting a basicmetal compound containing a metal element of the group 2B, 3B, 4B or 5Bof the periodic table with an acid group derived from at least one of PSand PPO, whereby an ionic bond between the acid and the base is formed.The ionic bond thus formed can bind different types of polymer chainstogether, so cross-linking structures are formed in the entire polymersconstituting the thermally resistant resin composition, whereby theglass transition temperature of the thermally resistant resincomposition is improved, involving the improvement of the heatresistance. From the respect of the improvement of heat resistance,preferably, ionic bonds may be formed on the acid groups derived fromboth of PS and PPO.

The basic metal compound to be used in the ionic bonding includes forexample water-soluble salts, hydroxides, halides, and organic acid saltssuch as acetate and lactate, of zinc (Zn) of the group 2B; aluminum(Al), gallium (Ga), indium (In) or thallium (Tl) of the group 3B;germanium (Ge), tin (Sn) or lead (Pb) of the group 4B; antimony (Sb) orbismuth (Bi) of the group 5B. Specifically, Zn is preferable from therespect of improving the heat resistance, while Al is also preferablefrom the respect of global environmental concerns after disposal. Fromthe finding that excellent miscibility is exhibited at a mixing ratio inweight of PS and PPO of around 50/50, preference is given to Ge, Sn, Pb,Sb or Bi.

If the amount of such basic metal compound to be used relative to anacid group is too less, the effect of improving the heat resistance isnot satisfactory; if the amount is too much, the insulating propertiesand humidity resistance of the thermally resistant resin composition aredeteriorated. Thus, the amount is at a ratio of preferably 1/10 to 10/1fold in mole, more preferably 1/5 to 5/1 fold in mole.

The acid group derived from at least one of PS and PPO includes forexample sulfonic acid group, OPO(OH)₂, PO(OH)₂, carboxyl group orphenolic hydroxyl group. Preference is given to sulfonic acid group orcarboxyl group in particular.

The PS prior to neutralization, namely the PS prior to the ionicbonding, has a chemical structure specifically represented by theformula (1);

(wherein R¹ is hydrogen atom or methyl group; X is hydrogen atom or anacid group selected from the group consisting of sulfonic acid group,carboxyl group, PO(OH)₂, OPO(OH)₂ and hydroxyl group; and “n” is apolymerization degree, provided that X is an acid group for the singleuse of PS). R¹ is preferably hydrogen atom in particular; X ispreferably sulfonic acid group or carboxyl group from the respect ofready introduction and reactivity with a basic metal compound.

The weight average molecular weight (Mw) of the PS to be used inaccordance with the present invention is preferably 50,000 to 400,000,more preferably 190,000 to 350,000 because the heat resistance isinsufficient if the weight is too less while the moldability isinsufficient if the weight is too much.

The PPO prior to neutralization, namely the PPO prior to the ionicbonding, has a chemical structure specifically represented by theformula (2);

(wherein R² and R³ independently represent hydrogen atom, methyl group,or an acid group selected from the group consisting of carboxymethylgroup, sulfonic methyl group, —CH2PO(OH)₂, and —CH₂OPO(OH)₂; R⁴ and R⁵independently represent hydrogen atom, methyl group, or an acid groupselected from the group consisting of sulfoninc acid group, carboxylgroup, PO(OH)₂, and OPO(OH)₂ and hydroxyl group; and “1” is apolymerization degree). Specifically, R² and R⁴ are preferably methylgroup, while R⁴ and R⁵ are preferably sulfone group or carboxyl groupfrom the respect of ready introduction of an acid group into at leastone of the two and the reactivity with a basic metal compound.

The weight average molecular weight (Mw) of the PPO to be used inaccordance with the present invention is preferably 5,000 to 100,000,more preferably 10,000 to 80,000 because the heat resistance isinsufficient because of the decrease of the glass transition point (Tg)if the weight is too less while the moldability is insufficient if theweight is too much.

Additionally, a vinyl monomer represented by the formula 3 or butadienemay be contained in the PS within a range of no occurrence of thedeterioration of the advantages of the present invention.

(wherein R⁶ is hydrogen atom or methyl group; Y is tolyl group,ethylphenyl group, cyano group, chloromethyl- or bromomethylphenylgroup, chloro- or bromophenyl group, carboxyl group or loweralkoxycarbonyl group; and “m” is a polymerization degree).

The content of the acid group in the thermally resistant resincomposition (PS+PPO) is generally 0.1 to 50 molar %, preferably 1 to 35molar %, because the effect of improving the heat resistance is notsatisfactory if the content is too low while the water absorptivity ofthe thermally resistant resin composition is increased to causeinsufficient water resistance if the content is too high. In PS and PPOblended resin composition, when the content of an acid group ifintroduced into either one of PS and PPO is 2.5 molar % or more, or whenthe content of acid groups if introduced into both PS and PPO is 4.0molar % or more, the miscibility of both the resins is deteriorated.Good effects by the present invention are therefore obtained when acidgroups with these contents or more are introduced.

The ratio of PS and PPO contents in the resin composition of the presentinvention may be appropriately determined depending on the purpose foruse, the processing properties, the production cost and the like.Generally, the contents are as follows; the content of PS is 1 to 99% byweight, preferably 10% to 90% by weight, more preferably 20% to 80% byweight. Correspondingly, the content of PPO is generally 99% to 1% byweight, preferably 90 to 10% by weight, and more preferably 80% to 20%by weight. As has been described above, the content of PPO with a higherproduction cost can be remarkably lowered provided that the objectiveheat resistance is not changed compared with conventional heatresistance, whereby the production cost of the resin composition can bedecreased profoundly.

In addition to PS and PPO, resins with excellent miscibility with thesepolymers may be added to the thermally resistant resin composition ofthe present invention, for example ABS resins, polyolefin resins(polyethylene, polypropylene, etc.), nylon (polycaprolactam) resins,acrylic resins (ethylene-acrylic acid, etc.) within a range of nooccurrence of the deterioration of the advantages of the presentinvention, generally up to 20% by weight.

The thermally resistant resin composition of the present invention maybe produced as follows. Firstly, PS and PPO each introduced with an acidgroup are independently prepared by a routine method, which are thenmixed together and dissolved in a solvent such as tetrahydrofuran. Tothe resulting solution then was added an aqueous solution of a basicmetal compound at an amount required to neutralize the acid groupspresent in the PS and PPO, prior to sufficient agitation to neutralizethe acid groups to form ionic bonds. By removing the solvent from thesolution, the thermally resistant resin composition is produced.Otherwise, a basic metal compound is added to the melt PS and PPO eachwith an acid group introduced, prior to kneading, to recover thethermally resistant resin composition.

Because the resulting thermally resistant resin composition isthermoplastic, the composition may be processed into housings of avariety of forms for electric appliances, by molding, press molding andthe like. By utilizing the excellent heat resistance, additionally, thecomposition may be used as the materials for printed board.

The PS with ionic bonds formed by neutralizing the acid group of PS witha basic metal compound has got improved heat resistance compared withgeneral PSs. The PPO with ionic bonds formed by neutralizing the acidgroup of PPO with a basic metal compound has got improved heatresistance compared with general PPOs. Therefore, the PS or PPO withsuch ion bonds formed may be used singly so as to improve the heatresistance of a molded article of conventional PS or PPO of a generaltype.

As has been described above, the basic metal compound for single use ofPS or PPO with ionic bonds formed includes basic metal compoundscontaining a metal element of the group 2B, 3B, 4B or 5B. In such case,the acid group content in the PS is 0.1 to 50 molar %, preferably 2 to20 molar %, while the acid group content in the PPO is 0.1 to 50 molar%, preferably 1 to 20 molar %.

Description has been made insofar about the improvement of the heatresistance of the thermally resistant resin composition of PS and PPO.The method for improving the heat resistance is also significant as amethod for miscible preparation of PS with PPO, at least one of PS andPPO having been introduced with an acid group.

The present invention will be described in detail with reference toexamples.

In the following Examples and Comparative Examples, a polystyrene of amolecular weight (Mw) of about 280,000 manufactured by Aldrich, Co. wasused. Furthermore, a polyphenylene oxide (PPO) of a molecular weight(Mw) of about 35,000 was used.

EXAMPLE A1

Introduction of Sulfonic Acid Group Into PS

PS was dissolved in dichloroethane, and to the resulting solution wasadded a mixture solution of conc. sulfuric acid and acetic anhydride(1:1.2 in molar ratio) prior to agitation at 60° C. for reaction. Afterthe completion of the reaction, the reaction mixture was poured into hotwater, followed by washing and re-precipitation to dry the resultingprecipitate, to recover PSs each with sulfonation degrees (contents ofsulfone group in PS) of 4.0 molar %, 9.1 molar % and 20.0 molar %.Additionally, the sulfonation degree was controlled by the adjustment ofthe amounts of conc. sulfuric acid and acetic anhydride added.

EXAMPLE A2

Introduction of Carboxyl Group Into PS

Radical polymerization of styrene monomer, 4-vinyl benzoic acid and aradical polymerization initiator (benzoyl peroxide; manufactured byNippon Yushi, Co. Ltd.) was done in tetrahydrofuran in nitrogenatmosphere at 50° C. After the termination of the polymerization,re-precipitation with a greater volume of methanol was carried out torecover precipitate, which was then dried to yield carboxylicacid-modified PS at a carboxylate content of 2.5 molar % or 5.2 molar %.Herein, the carboxylate content was controlled with the amount of4-vinyl benzoic acid charged.

EXAMPLE A3

Introduction of Sulfonic Acid Group Into PPO

By the same procedures as those for the introduction of sulfonic acidgroup into PS, PPO with a sulfonation degree of 1.0 molar %, 2.7 molar%, 5.0 molar % or 7.1 molar % was recovered.

EXAMPLE A4

Introduction of Carboxyl Group Into PPO

To a tetrahydrofuran solution of PPO was added dropwise a given amountof n-butyl lithium in a hexane solution under nitrogen purge forreaction at 25° C., and the resulting solution was poured into dry iceto terminate the reaction. Acidifying the resulting mixture with dilutehydrochloric acid and re-precipitating the mixture with a greater volumeof hexane, the resulting precipitate was dried to recover carboxylicacid-modified PPO at a carboxylate content of 4.0 molar % or 5.0 molar%.

EXAMPLES A5 TO A17 AND COMPARATIVE EXAMPLES A1 to A6

Polymer materials comprising PS or PPO or both, with the compositionsshown in Tables 1 and 2, were dissolved in tetrahydrofuran, and to theresulting solutions was added an aqueous solution of a neutralizationequivalent of a basic metal compound (zinc acetate in water sol.,aluminium lactate in water sol., antimony trichloride in acetonesolution, stannic chloride (SnCl₄) in water sol., to neutralize the acidgroup in PS or PPO or both.

After the neutralization, the solvent was removed from the solutions,followed by drying, to recover thermally resistant resin compositions of

EXAMPLES A5 TO A17 AND COMPARATIVE EXAMPLES A1 to A6.

The resulting resin compositions of Examples A5 to A17 and ComparativeExamples A1 to A6 were molded into a plate of a 0.3-mm thickness bymeans of a high-temperature press at 260° C. and 9.8 Mpa. The glasstransition temperatures (Tg) thereof were determined by measuring thetemperature elevation rate at 20° C. per minute by means of adifferential scanning calorie analyzer (product name; DSC-7,manufactured by Perkin Elmer Co. Ltd.). Tables 1 and 2 show the results.

Tables 1 and 2 show additionally the glass transition points (Tgs) ofblank PS with neither acid group nor ionic bonding (Comparative ExampleA1), PS with an ionic bond formed by using sodium hydroxide in place ofa basic metal compound (Comparative Examples A2 and A3), blank PPO withneither acid group nor ionic bonding (Comparative Example A4), PPO withan ionic bond formed by using sodium hydroxide in place of a basic metalcompound (Comparative Example A5), and a blend of blank PS and blank PPO(Comparative Example A6).

In Tables 1 and 2, “S” in the acid group column means “sulfonic acidgroup”; “C” means “carboxyl group”.

TABLE 1 PS PPO Acid group Acid group Content Blended Content Blended(molar amount (molar amount Basic Tg Type %) (wt %) Type %) (wt %) metal(° C.) Comparative example A 1 — — 100 — — 0 — 103.5 A 2 S 4.0 100 — — 0Na 114.2 A 3 S 9.1 100 — — 0 Na 122.0 Example A 5 S 4.0 100 — — 0 Zn125.3 A 6 S 9.1 100 — — 0 Zn 140.7 A 7 S 20.0  100 — — 0 Zn 185.0 A 8 S20.0  100 — — 0 Al 181.5

TABLE 2 PS PPO Acid group Acid group Content Blended Content Blended(molar amount (molar amount Basic Tg Type %) (wt %) Type %) (wt %) metal(° C.) Comparative example A 4 — — — — — 100 — 209.4 A 5 — — — S 1.0 100Na 210.3 Example A 9 — — — S 1.0 100 Al 218.4 A 10 — — — S 2.7 100 Al225.3 A 11 — — — S 5.0 100 Zn 241.3 A 12 — — — C 4.6 100 Zn 236.4Comparative example A 6 — — 20 — — 80 — 184.0 Example A 13 S 4.0 20 — —80 Al 199.5 A 14 — — 20 S 2.7 80 Al 200.8 A 15 S 4.0 20 S 2.7 80 Zn212.7 A 16 S 4.0 20 S 2.7 80 Sb 208.5 A 17 S 4.0 20 S 2.7 80 Sn 207.0

Tables 1 and 2 indicate the following.

No ionic bond is formed in the PS of Comparative Example A1; an ionicbond is formed via an alkali metal hydroxide instead of any amphotericmetal compound in Comparative Examples A2 and A3. On the contrary, thePSs of Examples A5 to A8 with ionic bonds formed through the reaction ofbasic metal compounds containing metal elements of the group 2B or 3B ofthe periodic table have highly increased glass transition pointscompared with the PSs of Comparative Examples A1 to A3, which indicatesthat the heat resistance thereof is remarkably improved.

The results of Examples A5 to A7 indicate that the glass transitionpoint is elevated as the increase of the sulfonic acid group contentfrom 4.0 molar % to 20.0 molar %. The results of Examples A7 and A8indicate that zinc is superior to aluminium as the basic metal for thebasic metal compounds in terms of the improvement of heat resistance.

The results of Comparative Examples A4 and A5 and Examples A9 to A12indicate that the heat resistance of PPO can be greatly improved byconstituting the ion bond in PPO via amphoteric metals.

The results of Comparative Example A6 and Examples A13 to A17 indicatethat the thermally resistant resin compositions comprising a mixture ofPS and PPO can procure improved heat resistance if an ionic bond isformed in at least one of PS and PPO. Preferably, acid groups areintroduced into both of PS and PPO, in particular, to form an ionicbond.

EXAMPLES B1 TO B13 AND COMPARATIVE EXAMPLES B1 TO B14

Polymer materials comprising PS or PPO or both, with the compositionsshown in Tables 3 and 4, were dissolved in tetrahydrofuran, and to theresulting solutions was added an aqueous solution of a neutralizationequivalent of a basic metal compound (aluminium lactate, stannoussulfate, zinc acetate, antimony trichloride (in acetone solution,manganese acetate, cobalt acetate), to neutralize the acid group in PSor PPO or both.

After the neutralization, the solvent was removed from the solutions,followed by drying, to recover thermally resistant resin compositions ofExamples B1 to B13 and Comparative Example B1 to B14.

The resulting resin compositions of Examples B1 to B13 and ComparativeExamples B1 to B14 were molded into a plate of a 0.3-mm thickness bymeans of a high-temperature press at 260° C. and 9.8 Mpa. The glasstransition temperatures (Tg) thereof were determined by measuring thetemperature elevation rate at 20° C. per minute by means of adifferential scanning calorie analyzer (product name; DSC-7,manufactured by Perkin Elmer Co. Ltd.). Tables 3 and 4 show the results.

Tables 3 and 4 show additionally the glass transition points (Tgs) of ablend of blank PS and blank PPO both with neither acid group nor ionicbonding (Comparative Example B1, B5, B10, and B12), a blend of PS andPPO both with an ionic bond formed by using sodium hydroxide in place ofa basic metal compound (Comparative Examples B2 , B6, B8, and B13), ablend of PS and PPO both with an ionic bond formed by using manganeseacetate in place of a basic metal compound (Comparative Examples B3, B7and B9), a blend of PS and PPO both with an ionic bond formed by usingcobalt acetate in place of a basic metal compound (Comparative ExamplesB4 and B11).

In Tables 3 and 4, furthermore, “S” in the acid group column means“sulfonic acid group”; “C” means “carboxyl group”.

TABLE 3 PS PPO Acid group Acid group Content Blended Content Blended(molar amount (molar amount Basic Tg Type %) (wt %) Type %) (wt %) metal(° C.) Comparative example B 1 — — 60 — — 40 — 142.1 B 2 S 4.0 60 — — 40Na 142.3 214.9 B 3 S 4.0 60 — — 40 Mn 141.7 208.6 B 4 C 2.5 60 — — 40 Co133.2 196.0 Example B 1 S 4.0 60 — — 40 Sn 152.8 B 2 S 4.0 60 — — 40 Sb152.1 Comparative example B 5 — — 40 — — 60 — 161.20 B 6 S 9.1 40 — — 60Na 149.6 214.9 B 7 S 9.1 40 — — 60 Mn 148.3 207.8 Example B 3 S 9.1 40 —— 60 Sn 178.3 B 4 S 9.1 40 C 5.0 60 Al 183.2 B 5 S 9.1 40 — — 60 Sb175.1 Comparative example B 8 S 9.1 40 S 2.7 60 Na 152.1 212.4 Example B6 C 2.5 40 C 5.0 60 Pb 184.2 B 7 S 9.1 40 S 2.7 60 Sb 180.2

TABLE 4 PS PPO Acid group Acid group Content Blended Content Blended(molar amount (molar amount Basic Tg Type %) (wt %) Type %) (wt %) metal(° C.) Comparative example B 9 S 20.0  60 — — 40 Mn 180.1 215.0 ExampleB 8 S 20.0  60 — — 40 Sn 198.2 B 9 S 4.0 60 — — 40 Sn 170.2 B 10 S 4.060 — — 40 Sb 173.5 Comparative example B 10 — — 20 — — 80 — 181.2 B 11 S4.0 20 — — 80 Co 189.7 213.5 Example B 11 S 4.0 20 — — 80 Al 218.1Comparative example B 12 S — 80 — — 20 — 121.8 B 13 S 4.0 80 — — 20 Na123.5 193.6 Example B 12 S 4.0 80 — — 20 Pb 145.1 Comparative example B14 — — 60 S 7.1 40 Na 121.8 Example B 13 — — 60 S 7.1 40 Sn 162.1

Tables 3 and 4 indicate the following.

Those of Examples B1 to B13 produced by blending together PS and PPO atleast one of which has an acid group, and neutralizing the acid groupwith a basic metal compound containing a metal element of the group 3B,4B or 5B of the periodic table have individually a single glasstransition point because of good miscibility, as is observed in those ofComparative Examples B1, B5, B10 and B12 produced by blending togetherPS and PPO with no acid group. Furthermore, the glass transition pointsthereof are elevated, which indicates the improvement of the heatresistance.

Alternatively, those of Comparative Examples B2 to B4, B6 to B9, B11 andB13 in which neutralization was performed with metal compoundscontaining not a metal element of the group 3B, 4B and 5B but Na, Mn orCo cannot acquire satisfactory miscibility, to consequently haveindividually two glass transition points. In such case, the heatresistance of the blends depends on the lower glass transition point.

For reference, the dynamic elastic moduli (tan δ) of the resincompositions of Examples B3, Comparative Examples B5 and B6 vstemperature were measured at a temperature elevation rate of 5°C./minute and at a frequency of 1 Hz with a viscoelasticity analyzer(SOLID ANALYZER RSRA2, manufactured by RHEOMETRIC CO.). The results areshown in FIG. 1. FIG. 1 indicates that the composition of Example B3produced by blending PPO into PS with an acid group and neutralizing theacid group with stannous sulfate has a single glass transition point asis observed in the composition of Comparative Example B5 in which PS andPPO both with no acid group are blended together, which indicates thatthe miscibility thereof is excellent. Additionally, it is indicated thatthe glass transition point is elevated, involving the improvement of theheat resistance. The composition of Comparative Example B6 neutralizedwith sodium hydroxide has two glass transition points, which indicatesinsufficient miscibility.

What is claimed is:
 1. A polystyrene compound having an acid group andbeing represented by the following formula (1) wherein the acid group isneutralized with a neutralization amount of basic metal compoundeffective to neutralize the acid group, the basic metal compoundcontaining a metal selected from the group consisting of Al, Ga, In, Tl,Ge, Sn, Pg, Sb and Bi;

wherein R¹ is hydrogen atom or methyl group; X is an acid group selectedfrom the group consisting of PO(OH)₂ and OPO(OH)₂; and “n” is apolymerization degree, the polystyrene compound having a weight averagemolecular weight of from about 50,000 to about 400,000 and comprisingfrom about 2 to about 15 mol % of the acid functional group.
 2. Apolystyrene compound according to claim 1, wherein the basic compoundcontains Al.
 3. A polystyrene compound according to claim 1, wherein thebasic compound contains Ge, Sn, Pb, Sb or Bi.
 4. A polystyrene compoundaccording to claim 1, wherein the acid group is sulfonic (acid) groupOPO(OH)₂, PO(OH)₂, carboxyl group or phenolic hydroxyl group.